Process for the improvement of nickel



Feb 23,1932, A. BURKHARDT 347944.

. PROCESS FOR THE IIZMPROVIEIIAENTI or NICKEL Filed March 1s,v 1931' PatentedlFeb. 23, 1932 UNITED. STATES PATENT OFFICE ARTHUR B'URKEABM, OF FRANKFORT ON-THE MAIN, GERMANY, ASSIGNOB TO AMERICAN LURGI CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK Application filed March 16,

The invention relates to a process for the improvement of nickel and nickel-containing alloys.- The process is especially adapted to increase the tensile strength and elongation of pure nickel and nickel-containing steel alloys, so that bars and castings can be produced therefrom easily amenable to treatment when warm.

The process consists of a method of binding the sulphur that is present in the metal by addition of an agent. It is known that even a very low'percentage of sulphur produces extreme brittleness in nickel and nickel containing alloys. This sulphur is present when the nickel is stiffened in the form of little strings bordering the nickel crystals. Herctofore it has been proposed to desulphurize the nickel by the'addition of magnesium before casting. It was believed that the addition of the magnesium affected a degasification of the molten mass, which is not correct.

' The ma nesium does indeed combine with thebars and castings. The segregation of then added to the fused nickel.

"such large particles is especially ob'ectionable in the drawin of nickel sheets, ecause the round nests o the magnesium-sulphide inclusions are drawn to thin dark streaks.

Now if the nickel or nickel alloys are treated when fused with small uantities of lithium, a lithium-sulphide is ormed, and remains in the nickel as verytiny point-like inclusions. The tensile strength, elongation, compressibility of the metal are thus imroved.

The best way-of adding'the lithiumis in combination with magnesium. This addition is successful if a lithium magnesium alloy of, say, 15% lithium is prepared and By this method a considerable saving in the consumption of lithium is attained without changing the" favorable distributionof the PROCESS FOR THE IMPROVEMENT OF NICKEL 1931. Serial in 523,152.

precipitated sulphur compound in the form of very small inclusions. A greater improvement as to the mechanical qualities of the nickel is achieved by the lithium magnesium alloy than would be the case with pure lithium. Figure No. 2 shows nickel when treated with the lithium magnesium alloy. For example, nickel containing .08% sulphur shows a hardness when treated with magnesium'alone' of 102, and when treated with an alloy of magnesium containing 15%. lithium a hardness of 118. The compressibility of nickel containing .08% sulphur after the addition of .01% lithium is 36%, and after addition of .1% of an alloy of magnesium containing 15% lithium the compressibility is increased up to The quantity of lithium required will vary widely dependent upon the character or purity of the metal treated. The quantity should be adjusted so that as little as possible of lithium or magnesium remains unconsumed and allo ed with the nickel. The quantity require cannot really be determined by analysis but is best determined by test upon small batches of the metal under treatment, using different amounts until the desired effect is obtained. It may be said that the addition of lithium in quantities of the order of .0001% to .05% of lithium and to .3.% magnesium have been found to be suitable.

If the nickel has a high content of oxygen in addition to the content of sulphur, deoxidation can be eifected before adding lithium. This doxidation can also be obtained either by the lithium or magnesium lithium alloy, or to economize this medium by other deoxidizers, such as phosphorous or silicon which are known per se.

I claim 1.Process for the improvement of the mechanical qualities of nickel and nickel alloys containing sulfur which comprises adding thereto while in the molten state an agent comprising lithium which serves to bind the sulfur content thereof.

2. Process for the improvement of the mechanical qualities of nickel and nickel alloys containing sulfur which comprises converting the strings of sulfur at the crystal] boundaries thereof into minute globular inclusions by the addition to the molten metal of an agent comprising lithium.

3. Process for the improvement of the mechanical qualities of nickel and nickel alloys containing sulfur as defined in claim 1 in which the agent is an alloy of lithium and magnesium.

4. Process for the improvement of the mechanical qualities of nickel and nickel alloys containing sulfur as defined in claim 1 in which the agent is an alloy of lithium and magnesium containing about 15% of lithium. 5. Process for the improvement of the mechanical qualities of nickel and nickel. al-

loys containing sulfur as defined in claim 1 in which the agent is an alloy of lithium and magnesium in such proportions to each other and is added to themetal in such quantity that about .0001% to .05% of lithium and up to about .3% of magnesium are supplied.

6. Process for the improvement of the mechanical qualities ofmickel and nickel alloys containing. sulfur as defined in claim 1 in which the agent is an alloy of lithium and magnesium and is added to the metal in such amount that no substantial quantity thereof is left in the metal after reaction thereof with I the sulfur content of the metal.

In testimony whereof, I aflix my signature.

ARTHUR BURKHARDT. 

